Linux Virtualization - Mar 2023 - [PATCH v3] virtio-net: Fix probe of virtio-net on kvmtool

On Fri, Mar 03, 2023 at 04:46:03PM -0800, Jakub Kicinski
wrote:
> On Thu, 2 Mar 2023 04:48:38 -0500 Michael S. Tsirkin wrote:
> > > Looks not the core can try to enable and disable features
according to
> > > the diff between features and hw_features
> > > 
> > > static inline netdev_features_t netdev_get_wanted_features(
> > >         struct net_device *dev)
> > > {
> > >         return (dev->features & ~dev->hw_features) |
dev->wanted_features;
> > > }
> > 
> > yes what we do work according to code.  So the documentation is wrong
then?
> 
> It's definitely incomplete but which part are you saying is wrong?
So it says:
  2. netdev->features set contains features which are currently enabled
     for a device.

ok so far.
But this part:

  This should be changed only by network core or in
     error paths of ndo_set_features callback.

seems to say virtio should not touch netdev->features, no?

-- 
MST

On Sun, 5 Mar 2023 04:53:58 -0500, "Michael S. Tsirkin" <mst at
redhat.com> wrote:
> On Fri, Mar 03, 2023 at 04:46:03PM -0800, Jakub Kicinski wrote:
> > On Thu, 2 Mar 2023 04:48:38 -0500 Michael S. Tsirkin wrote:
> > > > Looks not the core can try to enable and disable features
according to
> > > > the diff between features and hw_features
> > > >
> > > > static inline netdev_features_t netdev_get_wanted_features(
> > > >         struct net_device *dev)
> > > > {
> > > >         return (dev->features & ~dev->hw_features)
| dev->wanted_features;
> > > > }
> > >
> > > yes what we do work according to code.  So the documentation is
wrong then?
> >
> > It's definitely incomplete but which part are you saying is wrong?
>
> So it says:
>   2. netdev->features set contains features which are currently enabled
>      for a device.
>
> ok so far.
> But this part:
>
>   This should be changed only by network core or in
>      error paths of ndo_set_features callback.
>
> seems to say virtio should not touch netdev->features, no?

I think the "changed" here refers to the user's opening or closing
a function
by network core.

If the features contain a certain function, but hw_features does not include it
means that this function cannot be modified by user.


 *	struct net_device - The DEVICE structure.
 *   [....]
 *	@features:	Currently active device features
 *	@hw_features:	User-changeable features

Thanks.

>
> --
> MST
>
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